#include <iostream>
#include <cstring>
#include <cstdint>
#include <vector>

// =============== Windows ==============
#if defined(_WIN32) || defined(_WIN64)
#include <cstdint>
#include <ws2tcpip.h>
#include <winsock2.h>
#include "ws2ipdef.h"
#include <windows.h>
#pragma comment(lib, "ws2_32.lib")
#define close(sock) closesocket(sock)
typedef SOCKET socket_t;
#define INVALID_SOCKET_VALUE INVALID_SOCKET
using ushort = unsigned short;
// =========  Unix/Linux/Macos  =========
#else
#include <arpa/inet.h>
#include <sys/socket.h>
#include <unistd.h>
#include <ifaddrs.h> //ipv4
#include <netdb.h>   //ipv4
#include <sys/select.h>
#define INVALID_SOCKET_VALUE -1
typedef int             socket_t;
typedef struct sockaddr SOCKADDR;
#endif

using namespace std;

#pragma pack(push, 1)
struct Address {
	uint32_t ip;   // 网络字节序
	uint16_t port; // 网络字节序

	string ip_str() {
		char           buffer[INET_ADDRSTRLEN];
		struct in_addr addr;
		addr.s_addr = htonl(ip);
		if (inet_ntop(AF_INET, &addr, buffer, sizeof(buffer)) != nullptr) {
			return string(buffer);
		}
		return "";
	};

	string addr() {
		auto port_str = static_cast<int>(port);
		return ip_str() + ":" + to_string(port_str);
	}
};

inline Address createAddress(const char *ip, const uint16_t port) {
	struct in_addr addr;
	if (inet_pton(AF_INET, ip, &addr) != 1) {
		throw runtime_error("ip error");
	}

	Address result;
	result.ip   = ntohl(addr.s_addr);
	result.port = port;
	return result;
};
#pragma pack(pop)


// CRC 高位字节值表
static const uint8_t auchCRCHi[] = {0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, //
                                    0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, //
                                    0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, //
                                    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, //
                                    0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, //
                                    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, //
                                    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, //
                                    0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, //
                                    0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, //
                                    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, //
                                    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, //
                                    0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, //
                                    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, //
                                    0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, //
                                    0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, //
                                    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40};

// CRC 低位字节值表
static const uint8_t auchCRCLo[] = {0x00, 0xC0, 0xC1, 0x01, 0xC3, 0x03, 0x02, 0xC2, 0xC6, 0x06, 0x07, 0xC7, 0x05, 0xC5, 0xC4, 0x04, //
                                    0xCC, 0x0C, 0x0D, 0xCD, 0x0F, 0xCF, 0xCE, 0x0E, 0x0A, 0xCA, 0xCB, 0x0B, 0xC9, 0x09, 0x08, 0xC8, //
                                    0xD8, 0x18, 0x19, 0xD9, 0x1B, 0xDB, 0xDA, 0x1A, 0x1E, 0xDE, 0xDF, 0x1F, 0xDD, 0x1D, 0x1C, 0xDC, //
                                    0x14, 0xD4, 0xD5, 0x15, 0xD7, 0x17, 0x16, 0xD6, 0xD2, 0x12, 0x13, 0xD3, 0x11, 0xD1, 0xD0, 0x10, //
                                    0xF0, 0x30, 0x31, 0xF1, 0x33, 0xF3, 0xF2, 0x32, 0x36, 0xF6, 0xF7, 0x37, 0xF5, 0x35, 0x34, 0xF4, //
                                    0x3C, 0xFC, 0xFD, 0x3D, 0xFF, 0x3F, 0x3E, 0xFE, 0xFA, 0x3A, 0x3B, 0xFB, 0x39, 0xF9, 0xF8, 0x38, //
                                    0x28, 0xE8, 0xE9, 0x29, 0xEB, 0x2B, 0x2A, 0xEA, 0xEE, 0x2E, 0x2F, 0xEF, 0x2D, 0xED, 0xEC, 0x2C, //
                                    0xE4, 0x24, 0x25, 0xE5, 0x27, 0xE7, 0xE6, 0x26, 0x22, 0xE2, 0xE3, 0x23, 0xE1, 0x21, 0x20, 0xE0, //
                                    0xA0, 0x60, 0x61, 0xA1, 0x63, 0xA3, 0xA2, 0x62, 0x66, 0xA6, 0xA7, 0x67, 0xA5, 0x65, 0x64, 0xA4, //
                                    0x6C, 0xAC, 0xAD, 0x6D, 0xAF, 0x6F, 0x6E, 0xAE, 0xAA, 0x6A, 0x6B, 0xAB, 0x69, 0xA9, 0xA8, 0x68, //
                                    0x78, 0xB8, 0xB9, 0x79, 0xBB, 0x7B, 0x7A, 0xBA, 0xBE, 0x7E, 0x7F, 0xBF, 0x7D, 0xBD, 0xBC, 0x7C, //
                                    0xB4, 0x74, 0x75, 0xB5, 0x77, 0xB7, 0xB6, 0x76, 0x72, 0xB2, 0xB3, 0x73, 0xB1, 0x71, 0x70, 0xB0, //
                                    0x50, 0x90, 0x91, 0x51, 0x93, 0x53, 0x52, 0x92, 0x96, 0x56, 0x57, 0x97, 0x55, 0x95, 0x94, 0x54, //
                                    0x9C, 0x5C, 0x5D, 0x9D, 0x5F, 0x9F, 0x9E, 0x5E, 0x5A, 0x9A, 0x9B, 0x5B, 0x99, 0x59, 0x58, 0x98, //
                                    0x88, 0x48, 0x49, 0x89, 0x4B, 0x8B, 0x8A, 0x4A, 0x4E, 0x8E, 0x8F, 0x4F, 0x8D, 0x4D, 0x4C, 0x8C, //
                                    0x44, 0x84, 0x85, 0x45, 0x87, 0x47, 0x46, 0x86, 0x82, 0x42, 0x43, 0x83, 0x41, 0x81, 0x80, 0x40};

uint16_t CRC16(const char *ptr, int len) {
	uint8_t uIndex;
	uint8_t crcH = 0xFF; // H CRC 字节
	uint8_t crcL = 0xFF; // L CRC 字节
	while (len--) {
		uIndex = crcH ^ *ptr++; // 计算CRC
		crcH   = crcL ^ auchCRCHi[uIndex];
		crcL   = auchCRCLo[uIndex];
	}
	return ((crcH << 8) | crcL);
}

// ========================================================================
// 严格1字节对齐
#pragma pack(push, 1)
struct Message {
	uint16_t magic;      // 魔数标识(快速识别协议等)
	Address  routers[4]; // 路有记录,结构如：{uint32_t ip;uint16_t port; }
	uint16_t data_len;   // 载荷长度
};
#pragma pack(pop)

// typedef uint16_t Magic;

struct MagicInfo {
	bool    direct; // 0:业务报文；1:网关报文(直达)
	uint8_t flag;
	uint8_t cmd;
};

// 01000010
// 10000000
MagicInfo parse_magic(uint16_t magic) {
	MagicInfo mi;
	uint8_t   h8 = (magic >> 8) && 0xFF; // 取高8位(如：10000010 00000110 >> 00000000 10000010)
	mi.direct    = (h8 & 0x80) == 0;     // 10000010取最高1位，判断是否是0
	mi.flag      = h8 & 0x7F;            // 取低7位
	mi.cmd       = magic & 0xFF;         // 00000110, 即：6
	return mi;
}

uint16_t build_magic(bool direct, uint8_t flag, uint8_t cmd) {
	uint8_t h8 = (direct ? 0x00 : 0x80) | (flag & 0x7F);
	return (static_cast<uint16_t>(h8) << 8 | (cmd & 0xFF));
}

enum Msg_Type : uint8_t {
	SGW_SUMMON    = 0x00, // 网关召唤
	SGW_SYNCHRO   = 0x01, // 服务同步
	SGW_HEARTBEAT = 0x02, // 网关心跳
	SGW_REQUEST   = 0x03, // 服务请求
	SGW_RESPONSE  = 0x04, // 服务响应
	API_PING      = 0x10, // Ping
	API_LOGIC     = 0x11, // API接口
};

void udp_sender(const char *ip, int port, bool direct) {
	int fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
	if (fd < 1) {
		std::cerr << "Create socket failed" << std::endl;
		return;
	}

	// 设置服务器地址
	struct sockaddr_in serverAddr;
	serverAddr.sin_family = AF_INET;
	serverAddr.sin_port   = htons(port);
	inet_pton(AF_INET, ip, &serverAddr.sin_addr);

	const char *data     = direct ? "hello from direct" : "hello from agent";
	size_t      data_len = strlen(data);

	Address routers[4] = {};
	if (!direct) {
		routers[0] = {inet_addr("192.168.0.1"), htons(8080)};
		routers[1] = {inet_addr("192.168.0.2"), htons(8081)};
	}

	size_t base_len   = sizeof(Message);
	size_t router_len = direct ? 0 : sizeof(routers);
	size_t total      = base_len + router_len + data_len + sizeof(uint16_t); // base + router + data + crc16

	std::vector<char> buf(total);
	Message          *msg = reinterpret_cast<Message *>(buf.data());

	msg->magic        = htons(build_magic(direct, 0x33, 0xAA));
	msg->data_len     = htonl(data_len);
	char *current_ptr = buf.data() + base_len;
	if (!direct) {
		memcpy(current_ptr, routers, router_len);
		current_ptr += router_len;
	}
	memcpy(current_ptr, data, data_len);
	size_t n = sendto(fd, buf.data(), total, 0, reinterpret_cast<sockaddr *>(&serverAddr), sizeof(serverAddr));
	cout << "Send: " << n << endl;
	close(fd);
}

void udp_receiver(uint16_t port) {
	int sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
	if (sockfd < 1) {
		std::cerr << "Create socket failed" << std::endl;
		return;
	}

	sockaddr_in local{};
	local.sin_family      = AF_INET;
	local.sin_addr.s_addr = INADDR_ANY;
	local.sin_port        = htons(port);

	bind(sockfd, reinterpret_cast<sockaddr *>(&local), sizeof(local));
	std::vector<char> buf(1024);
	sockaddr_in       src_addr{};
	socklen_t         src_len = sizeof(src_addr);
	cout << "usp server is running: " << port << endl;

	size_t recv_len = recvfrom(sockfd, buf.data(), buf.size(), 0, reinterpret_cast<sockaddr *>(&src_addr), &src_len);
	if (recv_len < sizeof(Message)) {
		std::cerr << "Message is too short" << std::endl;
		return;
	}

	cout << "received: " << recv_len << endl;
	Message *msg = reinterpret_cast<Message *>(buf.data());
	auto     mi  = parse_magic(msg->magic);
	cout << "cmd: " << mi.cmd << endl;
	cout << "direct: " << mi.direct << endl;
	cout << "flag: " << mi.flag << endl;
	cout << "data_len: " << msg->data_len << endl;
}

// g++ -std=c++11 -pthread -o message_receiver.exe message_receiver.cpp -lws2_32
int main() {
#ifdef _WIN32
	WSADATA wsaData;
	if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0) {
		std::cerr << "WSAStartup failed..." << std::endl;
		return 1;
	}
#endif
	// udp_sender("127.0.0.1", 8080, true);
	udp_receiver(8080);

#ifdef _WIN32
	WSACleanup();
#endif
	return 0;
}
